This invention relates to the provision of improved automatic pattern-controlled mechanism for feeding and at the same time guiding a workpiece relative to an operating tool.
More especially the invention is concerned with providing simplified mechanism for automatically controlling incremental feeding and guidance of a flexible sheet-like workpiece in the successive intervals when an operating tool, for instance a sewing needle, is inoperative whereby a desired operating path is established according to some predetermined pattern or curvature-controlling means such as a workpiece edge.
It is well known in the machine tool industry to predetermine, by means of numerical or other data control, an operating path of a tool with respect to a rigid workpiece. In the case of operations upon lighter-weight work and flexible sheet materials, where it is usually preferable to move the work relative to a tool, rather than vice-versa, in establishing an operating path, several automatic work guidance approaches are also known and include, for example, those disclosed in U.S. Letters Pat. No. 2,979,745 to Schaefer et al; 3,034,781 to Touchman et al; and 3,080,836 to Clemens et al.
Automatic guidance of a flexible, even flimsy workpiece is often important to industry in expeditiously producing neat, uniform, and lower cost products. Difficulty arises in overcoming inertia of the workpiece so that precise increments of linear feed in a single direction and/or as required by changes in direction can be efficiently accomplished and without interfering with an operation or process as the work is appropriately moved. It has been proposed in the prior art to provide a rectilinear feeding of the work by one intermittently or continuously operative feed means in combination with a separate steering means which would exert guidance torque when the feed means was inoperative or ineffectual. It is also old to provide, as disclosed in U.S. Letters Pat. No. 3,650,229 to Rovin, in combination with a feed dog mechanism of the orbital type, a rotary friction means operable on the opposite side of the workpiece from the feed dog for varying the course of sheet material. Yet another automatic guidance mechanism for a sewing machine is disclosed in U.S. Letters Pat. No. 3,693,561 to Hrinko et al wherein a feed dog operates on one side of a workpiece to advance it relative to a needle, and on the opposite side of reversibly rotative guide ring surrounding the needle is responsive to edge sensing means for orienting the work during non-feeding and as it is being sewn.
Commerical acceptability of the prior art approaches to automatic work guidance means for sewing machines and other types operable on sheet material has, for various reasons, not hitherto proven generally practicable.